Date of Completion


Document Type

Honors College Thesis


Animal and Veterinary Sciences

Thesis Type

College of Arts and Science Honors, Honors College

First Advisor

John Barlow


mastitis, organic dairy, Staphylococcus aureus, essential oil, minimum inhibitory concentration (MIC)


Staphylococcus aureus causes mastitis in dairy cattle, resulting in significant drops in production and profits for dairy farmers. Mastitis treatment and prevention is the leading cause of antimicrobial agent use on conventional dairies. As antimicrobial agent resistance to current penicillin-based treatments is on the rise, it is pertinent that alternative mastitis treatments are researched. Several studies have suggested that plant-derived essential oils (EO) could serve as alternative treatments and supplements for dairy farmers. However, significant deviations in results have been noted in studies determining the susceptibility of S. aureus to EO in antimicrobial susceptibility assays. This study compared the differences in susceptibility to Cinnamon Bark oil (CBO) of 48 different S. aureus isolates collected from 26 organic dairy farms in Vermont using 4 common antimicrobial assays: AD, BM, DD, and VP. In vitro, the same 48 S. aureus isolates produced significantly different CBO MIC values across each treatment but not amongst each other. On average, VP had the highest CBO MIC values, followed by DD, and AD. BM had the lowest CBO MIC values on average. This suggests that these differences of CBO MIC values for each isolate are attributed to the assay type. However, isolates in the VP assay had notably higher CBO MIC values. With consistent susceptibility to CBO recorded for all isolates among all assays, plant-derived EO have the potential to supply an equitably effective, sustainable alternative to conventional antimicrobials used against S. aureus.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.